1. Field of Invention
The present invention relates to a technical field of a substrate assembly that can be used as a TFT array substrate in an electrooptical device, such as a liquid-crystal device, and of an electrical test method of the substrate assembly. The present invention additionally relates to a technical field of an electrooptical device, such as a liquid-crystal device including such a substrate, of a manufacturing method of manufacturing the electrooptical device, and of a variety of pieces of electronic equipment including the electrooptical device.
2. Description of Related Art
In an electrooptical device, such as a thin-film transistor (TFT) driving liquid-crystal device, a thin-film transistor using high-temperature polysilicon, low-temperature polysilicon, or amorphous silicon, as a semiconductor layer is embedded in each pixel for switching controlling of the pixel on an insulator such as a glass substrate or a quartz substrate.
The polysilicon TFTs are generally excellent in transistor characteristics and power consumption. For this reason, satisfactory transistor characteristics and low power consumption features result if a peripheral circuit composed of such polysilicon TFTs is embedded in a peripheral area surrounding an image display area within which a number of pixel electrodes are arranged. The arrangement is advantageous because the TFTs within the image display area for pixel switching and TFTs forming the peripheral circuit are concurrently produced in the same manufacturing process.
On the other hand, the amorphous type TFTs are generally outperformed in transistor characteristics and power consumption properties by the polysilicon TFTs. For this reason, the peripheral circuit, fabricated of the amorphous silicon TFTs, typically fails to achieve satisfactory transistor characteristics and low power consumption. When the amorphous silicon TFTs are adopted as a pixel switching TFT, a technique in which an external integrated circuit (IC) is mounted in a peripheral area is widely accepted.